Density functional theory (DFT) calculations have been performed to study properties of chitosan (Chit) as a possible vehicle for carrying metformin (Met) drug. To this aim, the singular molecules of Met and Chit have been first optimized and sixteen possible bimolecular complexes have been subsequently constructed and optimized to obtaine the stabilized interacting structures. Two bimolecular complex have been seen as the most powerful interacting systems among all complexes. N5 and N8 atoms of Met are very much important atoms for interacting with Chit counterpart. Molecular parameters such as molecular orbital energies and dipole moments approved the effects of interations on both Chit and Met counterparts. Atomic scale quadrupole coupling constants demonstrated the effects of interactions on the electronic atomic sites. As a final remark, although the Chit could be used as a vehicle for Met; but further investigations are still required to see what’s happening inside the molecular systems.